Brazing Composition and Brazing Method for Superalloys

ABSTRACT

A brazing composition for the brazing of superalloys including a base material with at least one initial phase is provided. The initial phase has a solidus temperature that is below the solidus temperature of the base material and, above a certain temperature, forms with the base material and/or with at least one further initial phase at least one resultant phase, the solidus temperature of which is higher that the solidus temperature of the initial phases. Heat treatment takes place in two stages, wherein the temperature of the second heat treatment is preferably 800-1200° C. The brazing composition may likewise be of the type MCrAlX, and the power particles of the initial phase may be in the form of nanoparticles.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 12/525,588 filed onAug. 3, 2009. U.S. Ser. No. 12/525,588 is the US National Stage ofInternational Application No. PCT/EP2007/051100, filed Feb. 6, 2007 andclaims the benefit thereof.

FIELD OF INVENTION

The present invention relates to a brazing composition comprising a basematerial having a solidus temperature and at least one further phase.The invention also relates to a joining process which makes use of abrazing material of this type.

BACKGROUND OF INVENTION

Brazing compositions and joining processes of this type are used, forexample, in the production and refurbishment of components, inparticular components for high-temperature applications. In the case ofcomponents for high-temperature applications, such as turbine componentsin the hot-gas path of a turbine, damage caused by operation can onlyrarely be prepared using the customary welding and brazing processes,since the strength of the additional materials used is not sufficientfor ensuring the structural integrity in the high-temperatureenvironment.

Particular joining and repair processes using a material whichcohesively bonds to the parts to be joined or repaired are known fromthe prior art, for example from EP 1 258 545. In the brazing processdescribed therein, a brazing material having a similar composition tothe superalloy of a component is filled into a crack and heated to atemperature above the melting point of the brazing material over arelatively long period of time. Boron is added to the brazing materialin order to reduce the melting temperature. Other melting-temperaturereducers such as silicon are likewise known from the prior art. The heattreatment involves diffusion processes which reduce the concentration ofthe melting-point reducer in the brazing material by diffusion such thatthe brazing material solidifies. In this process, the diffusion leads toa concentration equilibrium with the surrounding superalloy material.The melting-point reducer which diffuses into the superalloy during theheat treatment may lead to brittle precipitates in the superalloy. Whenboron is used as the melting-point reducer, the precipitation of brittleborides may occur, for example, and these borides impair the mechanicalproperties of the component in the region of the repaired location.

SUMMARY OF INVENTION

An object of the present invention is therefore to provide a brazingcomposition and a joining process which reduce the formation of brittlephases in the material surrounding the joined location.

This object is achieved by means of a brazing composition as claimed inthe claims and by means of a process for cohesive joining as claimed inthe claims. The dependent claims contain advantageous refinements of theinvention.

A brazing composition according to the invention comprises a basematerial with a solidus temperature and at least one further phase,which represents an initial phase. In addition, the brazing compositionmay of course comprise further ingredients. The ingredients in thiscomposition may be present in particular in powder form. At least oneinitial phase has a solidus temperature which is below the solidustemperature of the base material. It is also selected so as to form atleast one resultant phase, completely or at least partially togetherwith the base material and/or together with at least one further initialphase, during heat treatment above a specific temperature, the solidustemperature of said resultant phase being higher than the solidustemperature of the initial phase or phases.

The brazing composition according to the invention makes joiningpossible without the use of melting-point-reducing additives such asboron or silicon. The brazing material according to the invention makesa process for cohesively joining components made from a base materialpossible. In the process, the brazing location provided with the brazingcomposition according to the invention is subjected to a first heattreatment. The temperature of the first heat treatment is selected suchthat the initial phase melts. Once the initial phase has melted, it maycompletely surround the base material. The joining location is thensubjected to a second heat treatment at a temperature which has theeffect that the initial phase, completely or preferably partiallytogether with the base material and/or together with the further initialphase, forms the at least one resultant phase. The temperature of thesecond heat treatment is selected, in particular, to be so high that theinitial phase reacts with at least some of the base material to form theresultant phase, which then has a higher solidus temperature than theinitial phase.

If the initial phase on the one hand and the base material and/or the atleast one further initial phase on the other hand are selected suchthat, after the second heat treatment, the resultant phase hasmechanical properties which are similar to the mechanical properties ofthe base material, it is possible to carry out reliable joining, forexample for repairing a component (such as closing a crack). Theresultant phase then ensures the corresponding mechanical properties inthe region of the joining location.

By way of example, nickel may be used as the base material of thebrazing composition and aluminum may be used as the initial phase. Inthis case, the temperature of the first heat treatment is in the rangebetween 660° C. (the melting point of aluminum) and about 800° C. If thealuminum particles are small enough, it is possible to reduce themelting point of the aluminum so that the aluminum already melts attemperatures below 660° C. The temperature of the second heat treatmentis in the range between about 800° C. and 1200° C., preferably in therange between 1000° C. and 1100° C. Hard nickel aluminide (Ni₃Al) faunsat this temperature. This nickel aluminide has a solidus temperaturewhich is comparable with the solidus temperature of superalloys and alsohas comparable mechanical properties. In order to compensate forpossible shrinking of the brazing composition during the second heattreatment, it may be useful to apply a pressure during this heattreatment.

In a suitable brazing composition with nickel as the base material andaluminum as the initial phase, the aluminum content is in particularless than 25% by weight, preferably less than 10% by weight.

Instead of being formed from nickel and aluminum, the brazingcomposition may also be formed from a so-called MCrAlX material, inwhich M stands for nickel, cobalt or iron and X stands for yttriumand/or silicon and/or at least one rare earth element. Particularly if Mstands for nickel, the advantages described with reference to nickel asthe base material and aluminum as the initial phase can alsosubstantially be achieved with the MCrAlX material.

In order to simplify the melting of the initial phase and in addition toassist simpler flow of the melted initial phase around the basematerial, the powder particles of the initial phase may be smaller thanthe powder particles of the base material.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, properties and advantages of the present inventionemerge from the description of exemplary embodiments which follows, withreference to the attached figures.

FIG. 1 shows, by way of example, a partial longitudinal section througha gas turbine.

FIG. 2 shows a perspective view of a rotor blade or guide vane of aturbomachine.

FIG. 3 shows a combustion chamber of a gas turbine.

FIG. 4 shows a highly diagrammatic view of a turbine blade or vane to berepaired.

FIG. 5 shows the turbine blade or vane from FIG. 4 after repair.

FIG. 6 shows a highly diagrammatic illustration of a two-part turbineblade or vane at the start of a joining process.

FIG. 7 shows the turbine blade or vane from FIG. 6 at the end of thejoining process.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows, by way of example, a partial longitudinal section througha gas turbine 100.

In the interior, the gas turbine 100 has a rotor 103 with a shaft 101which is mounted such that it can rotate about an axis of rotation 102and is also referred to as the turbine rotor.

An intake housing 104, a compressor 105, a, for example, toroidalcombustion chamber 110, in particular an annular combustion chamber,with a plurality of coaxially arranged burners 107, a turbine 108 andthe exhaust-gas housing 109 follow one another along the rotor 103.

The annular combustion chamber 110 is in communication with a, forexample, annular hot-gas passage 111, where, by way of example, foursuccessive turbine stages 112 form the turbine 108.

Each turbine stage 112 is formed, for example, from two blade or vanerings. As seen in the direction of flow of a working medium 113, in thehot-gas passage ill a row of guide vanes 115 is followed by a row 125formed from rotor blades 120.

The guide vanes 130 are secured to an inner housing 138 of a stator 143,whereas the rotor blades 120 of a row 125 are fitted to the rotor 103for example by means of a turbine disk 133.

A generator (not shown) is coupled to the rotor 103.

While the gas turbine 100 is operating, the compressor 105 sucks in air135 through the intake housing 104 and compresses it. The compressed airprovided at the turbine-side end of the compressor 105 is passed to theburners 107, where it is mixed with a fuel. The mix is then burnt in thecombustion chamber 110, forming the working medium 113. From there, theworking medium 113 flows along the hot-gas passage 111 past the guidevanes 130 and the rotor blades 120. The working medium 113 is expandedat the rotor blades 120, transferring its momentum, so that the rotorblades 120 drive the rotor 103 and the latter in turn drives thegenerator coupled to it.

While the gas turbine 100 is operating, the components which are exposedto the hot working medium 113 are subject to thermal stresses. The guidevanes 130 and rotor blades 120 of the first turbine stage 112, as seenin the direction of flow of the working medium 113, together with theheat shield elements which line the annular combustion chamber 110, aresubject to the highest thermal stresses.

To be able to withstand the temperatures which prevail there, they maybe cooled by means of a coolant.

Substrates of the components may likewise have a directional structure,i.e. they are in single-crystal form (SX structure) or have onlylongitudinally oriented grains (DS structure).

By way of example, iron-base, nickel-base or cobalt-base superalloys areused as material for the components, in particular for the turbine bladeor vane 120, 130 and components of the combustion chamber 110.

Superalloys of this type are known, for example, from EP 1 204 776 B1,EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949; thesedocuments faun part of the disclosure with regard to the chemicalcomposition of the alloys.

The blades or vanes 120, 130 may also have coatings which protectagainst corrosion (MCrAlX; M is at least one element selected from thegroup consisting of iron (Fe), cobalt (Co), nickel (Ni), X is an activeelement and stands for yttrium (Y) and/or silicon, scandium (Sc) and/orat least one rare earth element or hafnium). Alloys of this type areknown from EP 0 486 489 B1, EP 0 786 017 B1, EP 0 412 397 B1 or EP 1 306454 A1, which are intended to form part of the present disclosure withregard to the chemical composition.

A thermal barrier coating, consisting for example of ZrO₂, Y₂O₃-ZrO₂,i.e. unstabilized, partially stabilized or fully stabilized by yttriumoxide and/or calcium oxide and/or magnesium oxide, may also be presenton the MCrAlX.

Columnar grains are produced in the thermal barrier coating by suitablecoating processes, such as for example electron beam physical vapordeposition (EB-PVD).

The guide vane 130 has a guide vane root (not shown here), which facesthe inner housing 138 of the turbine 108, and a guide vane head which isat the opposite end from the guide vane root. The guide vane head facesthe rotor 103 and is fixed to a securing ring 140 of the stator 143.

FIG. 2 shows a perspective view of a rotor blade 120 or guide vane 130of a turbomachine, which extends along a longitudinal axis 121.

The turbomachine may be a gas turbine of an aircraft or of a power plantfor generating electricity, a steam turbine or a compressor.

The blade or vane 120, 130 has, in succession along the longitudinalaxis 121, a securing region 400, an adjoining blade or vane platform 403and a main blade or vane part 406 and a blade or vane tip 415.

As a guide vane 130, the vane 130 may have a further platform (notshown) at its vane tip 415.

A blade or vane root 183, which is used to secure the rotor blades 120,130 to a shaft or a disk (not shown), is formed in the securing region400.

The blade or vane root 183 is designed, for example, in hammerhead form.Other configurations, such as a fir-tree or dovetail root, are possible.

The blade or vane 120, 130 has a leading edge 409 and a trailing edge412 for a medium which flows past the main blade or vane part 406.

In the case of conventional blades or vanes 120, 130, by way of examplesolid metallic materials, in particular superalloys, are used in allregions 400, 403, 406 of the blade or vane 120, 130.

Superalloys of this type are known, for example, from EP 1 204 776 B1,EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949; thesedocuments form part of the disclosure with regard to the chemicalcomposition of the alloy.

The blade or vane 120, 130 may in this case be produced by a castingprocess, by means of directional solidification, by a forging process,by a milling process or combinations thereof.

Workpieces with a single-crystal structure or structures are used ascomponents for machines which, in operation, are exposed to highmechanical, thermal and/or chemical stresses.

Single-crystal workpieces of this type are produced, for example, bydirectional solidification from the melt. This involves castingprocesses in which the liquid metallic alloy solidifies to form thesingle-crystal structure, i.e. the single-crystal workpiece, orsolidifies directionally.

In this case, dendritic crystals are oriented along the direction ofheat flow and form either a columnar crystalline grain structure (Le.grains which run over the entire length of the workpiece and arereferred to here, in accordance with the language customarily used, asdirectionally solidified) or a single-crystal structure, i.e. the entireworkpiece consists of one single crystal. In these processes, atransition to globular (polycrystalline) solidification needs to beavoided, since non-directional growth inevitably forms transverse andlongitudinal grain boundaries, which negate the favorable properties ofthe directionally solidified or single-crystal component.

Where the text refers in general terms to directionally solidifiedmicrostructures, this is to be understood as meaning both singlecrystals, which do not have any grain boundaries or at most havesmall-angle grain boundaries, and columnar crystal structures, which dohave grain boundaries running in the longitudinal direction but do nothave any transverse grain boundaries. This second form of crystallinestructures is also described as directionally solidified microstructures(directionally solidified structures).

Processes of this type are known from U.S. Pat. No. 6,024,792 and EP 0892 090 A1; these documents form part of the disclosure with regard tothe solidification process.

The blades or vanes 120, 130 may likewise have coatings protectingagainst corrosion or oxidation e.g. (MCrAlX; M is at least one elementselected from the group consisting of iron (Fe), cobalt (Co), nickel(Ni), X is an active element and stands for yttrium (Y) and/or siliconand/or at least one rare earth element, or hafnium (Hf)). Alloys of thistype are known from EP 0 486 489 B1, EP 0 786 017 B1, EP 0 412 397 B1 orEP 1 306 454 A1, which are intended to form part of the presentdisclosure with regard to the chemical composition of the alloy.

The density is preferably 95% of the theoretical density.

A protective aluminum oxide layer (TGO=thermally grown oxide layer) isformed on the MCrAlX layer (as an intermediate layer or as the outermostlayer).

The layer preferably has a composition Co-30Ni-28Cr-8Al-0.6Y-0.7Si orCo-28Ni-24Cr-10Al-0.6Y. In addition to these cobalt-based protectivecoatings, it is also preferable to use nickel-based protective layers,such as Ni-10Cr-12Al-0.6Y-3Re or Ni-12Co-21Cr-11Al-0.4Y-2Re orNi-25Co-17Cr-10Al-0.4Y-1.5Re.

It is also possible for a thermal barrier coating, which is preferablythe outermost layer and consists for example of ZrO₂, Y₂O₃—ZrO₂, i.e.unstabilized, partially stabilized or fully stabilized by yttrium oxideand/or calcium oxide and/or magnesium oxide, to be present on theMCrAlX.

The thermal barrier coating covers the entire MCrAlX layer. Columnargrains are produced in the thermal barrier coating by suitable coatingprocesses, such as for example electron beam physical vapor deposition(EB-PVD).

Other coating processes are possible, for example atmospheric plasmaspraying (APS), LPPS, VPS or CVD. The thermal barrier coating mayinclude grains that are porous or have micro-cracks or macro-cracks, inorder to improve the resistance to thermal shocks. The thermal barriercoating is therefore preferably more porous than the MCrAlX layer.

Refurbishment means that after they have been used, protective layersmay have to be removed from components 120, 130 (e.g. by sand-blasting).Then, the corrosion and/or oxidation layers and products are removed. Ifappropriate, cracks in the component 120, 130 are also repaired. This isfollowed by recoating of the component 120, 130, after which thecomponent 120, 130 can be reused.

The blade or vane 120, 130 may be hollow or solid in form. If the bladeor vane 120, 130 is to be cooled, it is hollow and may also havefilm-cooling holes 418 (indicated by dashed lines).

FIG. 3 shows a combustion chamber 110 of a gas turbine. The combustionchamber 110 is configured, for example, as what is known as an annularcombustion chamber, in which a multiplicity of burners 107, whichgenerate flames 156, arranged circumferentially around the axis ofrotation 102 open out into a common combustion chamber space 154. Forthis purpose, the combustion chamber 110 overall is of annularconfiguration positioned around the axis of rotation 102.

To achieve a relatively high efficiency, the combustion chamber 110 isdesigned for a relatively high temperature of the working medium M ofapproximately 1000° C. to 1600° C. To allow a relatively long servicelife even with these operating parameters, which are unfavorable for thematerials, the combustion chamber wall 153 is provided, on its sidewhich faces the working medium M, with an inner lining formed from heatshield elements 155.

On the working medium side, each heat shield element 155 made from analloy is equipped with a particularly heat-resistant protective layer(MCrAlX layer and/or ceramic coating) or is made from material that isable to withstand high temperatures (solid ceramic bricks).

These protective layers may be similar to the turbine blades or vanes,i.e. for example MCrAlX: M is at least one element selected from thegroup consisting of iron (Fe), cobalt (Co), nickel (Ni), X is an activeelement and stands for yttrium (Y) and/or silicon and/or at least onerare earth element or hafnium (Hf). Alloys of this type are known fromEP 0 486 489 B1, EP 0 786 017 B1, EP 0 412 397 B1 or EP 1 306 454 A1,which are intended to faun part of the present disclosure with regard tothe chemical composition of the alloy.

It is also possible for a, for example, ceramic thermal barrier coatingto be present on the MCrAlX, consisting for example of ZrO₂, Y₂O₃—ZrO₂,i.e. unstabilized, partially stabilized or fully stabilized by yttriumoxide and/or calcium oxide and/or magnesium oxide.

Columnar grains are produced in the thermal barrier coating by suitablecoating processes, such as for example electron beam physical vapordeposition (EB-PVD).

Other coating processes are possible, e.g. atmospheric plasma spraying(APS), LPPS, VPS or CVD. Thermal barrier coating may include grains thatare porous or have micro-cracks or macro-cracks, in order to improve theresistance to thermal shocks.

Refurbishment means that after they have been used, protective layersmay have to be removed from heat shield elements 155 (e.g. bysand-blasting). Then, the corrosion and/or oxidation layers and productsare removed. If appropriate, cracks in the heat shield element 155 arealso repaired. This is followed by recoating of the heat shield elements155, after which the heat shield elements 155 can be reused.

Moreover, a cooling system may be provided for the heat shield elements155 and/or their holding elements, on account of the high temperaturesin the interior of the combustion chamber 110. The heat shield elements155 are then, for example, hollow and may also have cooling holes (notshown) opening out into the combustion chamber space 154.

A first exemplary embodiment for the joining process according to theinvention is described below with reference to FIGS. 4 and 5. In thisexemplary embodiment, cohesive joining is used to repair a crack in aturbine blade or vane in the course of a refurbishment process.

FIG. 4 shows a highly diagrammatic view of the turbine blade or vane120, 130 in a section through the main blade or vane part 406, whichsection runs perpendicular to the surface 503 of the blade or vane wall501. The blade or vane wall 501 consists of a nickel-base superalloy ashas been described in the preceding paragraphs.

A crack 505 to be repaired in the course of the refurbishment processextends from the surface 503 into the blade or vane wall 501. For thispurpose, in a first step, the crack 505 is filled with a brazingcomposition which, in the present exemplary embodiment, contains nickel(Ni) as the base material and aluminum (Al) as a further phase. Thebrazing composition may also comprise further additives, but does notcontain any melting-point reducers. The crack 505 is filled with thebrazing composition 507 in such a way that some of the brazingcomposition protrudes from the surface 503 of the blade or vane wall501. This is used as a reservoir in order to compensate for the factthat the brazing composition shrinks during the repair. In order topress the brazing composition 507, which protrudes from the surface 503,into the crack 505 during the process, increased pressure is applied tothe location to be repaired during the process. By way of example, thispressure may be brought about mechanically or by an increasedatmospheric pressure during the process.

Both the nickel and the aluminum are present in powder form in thebrazing composition 507 according to the present exemplary embodiment,wherein the dimensions of the nickel particles are greater than those ofthe aluminum particles in the powder. As a result, the finer aluminumparticles can be distributed more effectively between the coarser nickelparticles.

Once the crack 505 has been filled with the brazing composition 507, theturbine blade or vane 120, 130 or at least that location of the blade orvane wall which is to be repaired is subjected to a first heattreatment. The temperature of the heat treatment is selected in such away that the aluminum particles melt but the nickel particles do not. Inother words, the temperature of the heat treatment is above the solidustemperature of aluminum (660° C.) and below the solidus temperature ofnickel (1455° C.). It should be noted at this juncture that it ispossible to reduce the solidus temperature somewhat if the particle sizeis in the nanometer range. In particular, the fine aluminum particlesmay therefore have especially small particle dimensions and this reducesthe solidus temperature of aluminum to below 660° C. This makes itpossible to increase the temperature range which can be used for thefirst heat treatment.

In the present exemplary embodiment, a temperature of about 750° C. isselected for the heat treatment. This makes it possible to ensure thatthe temperature is maintained at a sufficient distance from the meltingtemperature of the nickel and of the superalloy and that neither thenickel nor the nickel-base superalloy, from which the blade or vane wall501 is made, melts during this heat treatment (the solidus temperatureof nickel-base superalloys is about 1300° C., that of nickel is about1455° C.).

The turbine blade or vane or that location of the turbine blade or vanewhich is to be repaired is held at the temperature of the heat treatmentfor a specific time in order to ensure that all of the aluminum meltsand flows around all of the nickel particles and therefore surroundsthem.

The first heat treatment is followed by a second heat treatment,so-called diffusion heat treatment or so-called solution annealing. Thetemperature during the diffusion heat treatment is below the meltingtemperature of the nickel-base alloy and is about 1020° C.-1080° C. Theinitial phase, that is the aluminum, vanishes at these temperatures and,together with some of the nickel, forms a high-melting nickel aluminidephase, specifically Ni₃Al. The shrinkage of brazing material alreadymentioned above may occur particularly during the diffusion heattreatment. This is partly because aluminum diffuses into the surroundingnickel-base alloy and is therefore no longer available in the crack.Brazing composition from the brazing reservoir located on the surface503 of the blade or vane wall 501 is then pressed into the crack 505 bymeans of the applied pressure. The heat treatment is carried out untilthe aluminum has been converted largely and preferably completely intoNi₃Al.

After the heat treatment has finished, brazing material protruding fromthe surface 503 may be removed so as to obtain a smooth surface 503, asis illustrated in FIG. 5. In FIG. 5, the Ni₃Al phase is indicated byshort dashes. It extends beyond the crack into the nickel-base materialof the blade or vane wall. The selection of nickel and aluminum ascomponents of the brazing composition 507 makes it possible, in the caseof a blade or vane wall produced from a nickel-base superalloy, for theresultant phase (specifically Ni₃Al) to have mechanical propertiescomparable to those of the surrounding superalloy.

A second exemplary embodiment for the joining process according to theinvention is illustrated in FIGS. 6 and 7. By contrast with the joiningprocess from FIGS. 1 and 2, the process according to FIGS. 3 and 4 isnot a repair process but a process for bonding two separate parts 601,611. The process is carried out in the same way as the repair processdescribed, but it must be ensured that the brazing composition 607remains in the region between the two joining surfaces 613, 615. Thiscan be achieved, for example, by adhesion-increasing additives in thepowder of the brazing composition 607. However, it is also possible tomechanically hold the brazing composition 607 between the joiningsurfaces 613, 615, for example by sealing the periphery of the gapdelimited by the joining surfaces after said gap has been filled withbrazing material. The heat treatments to be carried out in the contextof the second exemplary embodiment correspond to those in the firstexemplary embodiment.

As in the first exemplary embodiment, the brazing composition may have aconfiguration which differs from merely consisting of nickel andaluminum. In particular, it is possible to use an MCrAlX composition asthe brazing composition. Even during the processing of brazingcompositions such as these, homogenization of the aluminum content leadsto an increase in the solidus point of the resultant phase.

In the described joining process, it is advantageous if not all of thenickel goes into the Ni₃Al phase. It is therefore desirable for thealuminum content, in comparison with nickel, not to exceed 25% byweight, preferably 10% by weight. This also applies when using theMCrAlX composition as the brazing composition.

1. A brazing composition, comprising: a base material with a firstsolidus temperature; and an initial phase with a second solidustemperature, wherein the second solidus temperature is below the firstsolidus temperature, wherein the initial phase is selected so that aresultant phase is formed, wherein during a heat treatment above aspecific temperature and when the initial phase is together with thebase material and/or the initial phase is together with a furtherinitial phase, a third solidus temperature of the resultant phase ishigher than the second solidus temperature or a fourth solidus phase ofthe further initial phase, and wherein the base material comprisesnickel and the initial phase is aluminum.
 2. The brazing composition asclaimed in claim 1, wherein the aluminum content is not more than 25% byweight.
 3. The brazing composition as claimed in claim 1, wherein thealuminum content is not more than 10% by weight.
 4. The brazingcomposition as claimed in claim 1, wherein the base material is nickel.5. The brazing composition as claimed in claim 1, wherein the brazingcomposition is a MCrAlX material, wherein M is the base material whichcomprises nickel, wherein M further comprises Co and/or Fe, and whereinX stands for yttrium and/or silicon and/or a rare earth element.
 6. Thebrazing composition as claimed in claim 1, wherein the brazingcomposition is present in a form of a powder mixture, and wherein theinitial phase has a first plurality of powder particles which aresmaller than a second plurality of powder particles of the basematerial.